Heat treatment may be performed when producing industrial products (see Patent Documents 1 to 3, for example). Patent Document 1 discloses a cooling nozzle for cooling a roll used when producing a metal sheet. Patent Document 2 discloses a cooling nozzle for cooling a metal sheet (strip) when producing the metal sheet. Patent Document 3 discloses a cooling nozzle for cooling a boat after diffusion treatment, the boat holding a semiconductor wafer when the diffusion treatment is being performed on the semiconductor wafer.